Field of the Invention
The invention is directed to ester-functional polysiloxanes and copolymers made therefrom.
Background of the Invention
Polycarbonate resins are well-known thermoplastic resins which have long been used in a variety of applications requiring resistance to impact. At low temperatures, generally lower than 20° C., polycarbonate becomes brittle and its utility is thus limited by this shortcoming. It is known that the low temperature impact strength of polycarbonate may be improved upon by the introduction (by copolymerization) of silicone blocks into the carbonate structure. U.S. Pat. Nos. 3,189,662; 3,419,634; 4,123,588; 4,569,970; 4,920,183 and 5,068,302 are noted to disclose relevant copolymers.
Relevant copolymers have been prepared in accordance with a melt blending process disclosed in U.S. Pat. No. 4,994,532. The process entails melt blending an aromatic polycarbonate resin and a polydiorganosiloxane having at least one functional carboxylic acid group.
Also relevant in the present context is U.S. Pat. No. 3,189,662 which disclosed a preparation method of polycarbonate siloxane co-monomer wherein the bisphenol moieties are bound to both the ends of polydimethylsiloxane. However hydrolysis of the siloxane monomer is likely to occur after polymerization due the presence of unstable silicone-oxygen bonds connecting Si atom and reactive moieties. The presence of hydrolytically unstable Si—O—C bonds leads to poor weather resistance and poor mechanical properties of the copolymer. While the foregoing silicone copolymers readily enter into a modification reaction because their hydroxyl groups are located at the para-position of the phenyl group, the polycarbonate resins produced are unstable and subject to hydrolysis because of the presence of Si—O—C linkage in the polymer chain. Such problems have been solved by developing siloxane monomers comprising of Si—C bonds which provides improved hydrolysis resistance. Monomers with improved heat stability and hydrolysis resistance having silicon alkyl bonds have been developed.
Three general paths to linear hydroxyaryloxy-terminated siloxanes of the following general structure are known in the prior art:
(A) U.S. Pat. No. 3,189,662 describes the reaction of chloroterminated polysiloxanes with bisphenolic compounds eliminating hydrochloric acid as the byproduct; (B) U.S. Pat. No. 4,732,949 describes the reaction of bisphenolic compounds with α,ω-bisacyloxypolydiorganosiloxanes in a solvent, and (C) U.S. Pat. No. 6,258,968 describes the reaction of bisphenolic compounds such as hydroquinone with a cyclic dialkyl siloxane such as octamethylcyclotetrasiloxane in a solvent, whereby an acid catalyst is used and water is removed from the reaction mixture by distillation.
As an alternative to hydroxyaryloxy-terminated siloxanes, carbonate-terminated siloxanes have also been used to prepare polysiloxane-polycarbonate block copolymers. For example, U.S. Pat. No. 5,504,177 describes a solvent-free melt process for preparing polydiorganosiloxane-polycarbonate block copolymers using Si—O—C free carbonate-terminated siloxanes of the general formula:

However, this path has the disadvantage that it requires the use of expensive p-allylphenolic precursors for the group R3 and the use of platinum catalysts, which adds to the cost of the process.
U.S. Pat. No. 4,895,965 describes a method for making carboxy aryl terminated organosiloxanes such as 1,1,3,3-tetramethyl-1,3-disiloxane diallylbis(benzoic acid) of general formula:
which is used for making polycarbonate-polysiloxane and polyester-siloxane copolymers.
U.S. Pat. No. 4,879,378 discloses polysiloxane containing sterically hindered phenol moieties, represented by general formula MDxD′yM, wherein

The sterically hindered phenol group attached to silicone atom via carbonyloxy containing linkage. This type of materials is used as stabilizers for polymers.
U.S. Pat. No. 5,292,850 discloses polymeric stabilizers with polysiloxane structure contain sterically hindered phenol groups and reactive groups capable of binding themselves to the polymer structure to be stabilized. These polymeric stabilizers are particularly suitable for applications which require the no extractability of additives due to solvents facts or soaps.
U.S. Pat. No. 8,426,532 describes the method of forming polycarbonate graft copolymers. Polycarbonate polymer or copolymer containing allyl groups provides the backbone for the graft copolymer, and pendant chains are attached to the copolymer through allyl groups.
However, polycarbonate-polysiloxanes disclosed in the prior art have the disadvantage that the precursor ester-functional polyorganosiloxanes possess non-suitable reactive terminal groups for interfacial polymerization. Additionally, the prior art manufacture of ester-functional polysiloxane requires the use of expensive precursors.
Accordingly, there is a need for cost effective novel polysiloxane copolymer compositions and polysiloxane polymer blends having an ester-functional polysiloxane precursor with suitable terminal reactive group for interfacial copolymerization. There is a need for ester functional hydroxyl aryl terminated siloxane compositions with improved thermal and hydrolytic stability. The present invention provides a cost effective method for producing ester-functional polysiloxanes. These ester-functional polysiloxanes when used in copolymers or polymer blends enhance low temperature impact resistance, flame resistance, hydrolytic and heat aging properties of the copolymers or polymer blends.